Hezbollah drone attack: How were Israeli air defences breached?

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Israel has launched an investigation into how its air defences on Sunday failed to thwart a Hezbollah drone attack on an army training base, a strike that killed at least four soldiers and injured more than 60 people.

The attack raises questions about Israel’s vaunted air defence systems, including the Iron Dome. The short-range system, while designed to counter rocket attacks, is also able to hit “one-way attack” drones – fixed-wing aircraft loaded with explosives that fly under conventional radars.

Israel has other systems for countering drones, including the Drone Dome, an array of small, powerful radars that provide 360-degree coverage, paired with an electronic jamming system and a high-powered laser.

Despite this technology, Hezbollah’s drone was able to hit its target at the training base of the Golani Brigade.

Iran-made drones

The type of drone used in the attack was the Mirsad unmanned aircraft, Hezbollah’s variant of the Iranian Ababil-T, the Times of Israel reported. The drone can travel 120km, putting the Israeli base at the limits of its range, assuming it came from the sea and travelled inland, as Israel claims.

It can, according to the Israeli Alma Research and Education Centre think tank, carry 40kg of explosives and weighs about 80kg.

“Most of the Iranian proxies, including Hezbollah, use similar models for drones,” said Seth Frantzman, author of Drone Wars: Pioneers, Killing Machines, Artificial Intelligence, and the Battle for the Future. "They don't have the capabilities to avoid modern air defences, but that doesn't mean they can't find complex routes that keep them away from air defences for part of their flight path."

This puts the Mirsad in the Nato class 2 drone category, as a relatively small attack drone that flies low. Videos of Ababil-T attacks show the aircraft flying at an altitude of couple of hundred metres.

By comparison, American Reaper drones, often used against the Taliban, are in the class 5 category. They weigh 4.7 tonnes and have a range of thousands of kilometres.

The low altitude and small size of the Hezbollah drones create a problem for older radar systems, which are designed to detect large missiles or aircraft at high altitude. Aircraft flying about 100 metres above ground can be missed, as the “horizon” of the radar is affected by the curvature of the Earth – not to mention hills blocking the beam.

Another problem is that most radars steer radio waves mechanically to cover an area, which has been compared to the movement of a torch. Drone attacks often come from unexpected angles, increasing the risk to the target, as the radar turns mechanically to find the threat.

The small size of the drones also means older radar systems could fail to detect it until it is too late.

Instead of acting like a searchlight, modern radars such as the Drone Dome’s MHR-42R use Active Electronically Scanned Array (AESA) technology to provide 360-degree coverage. Such radar have been compared to a light bulb.

The Drone Dome also has a camera with infrared technology that can reportedly monitor drones up to 8km away. The Iron Dome has similarly advanced sensors, including the ELM-2084 AESA radar, which also provides a “light bulb” effect.

According to reports on Monday, one of two Hezbollah drones launched in the attack was shot down over the sea, either by a plane or helicopter. The second dropped off Israel's radar.

That suggests the Israeli aircraft could have lacked a “look down/shoot down” radar, which is powerful enough to pick out low-flying objects from the surrounding “ground clutter” that would thwart other radars. Hezbollah claims it launched a rocket barrage at the same time as the drones, to keep the Iron Dome "busy".

Drone threat

The attack is similar to a deadly drone strike in January launched against US forces at a logistical support base in Jordan, known as Tower 22.

At the time, the site had been reinforced with electronic warfare equipment to jam the signal of attack drones, but had not been sent “hard kill” equipment for shooting drones down. It was also given an outdated TPS-75 radar, which has now been replaced by AESA systems.

Four US soldiers were killed and about 50 were injured. Better equipment had been prioritised for Iraq and Syria, where drone attacks were common, a US defence official told Politico.

In the Hezbollah attack on Sunday, it is possible the Israeli soldiers in the training base did not expect the attack so far from the front lines of the war, and that the defences were inadequate. Another possibility is that counter-drone systems were in place at the Israeli barracks, but human failure allowed the drones to slip through.

In the Ukraine war, there have been many attacks at training centres used by Russian and Ukrainian forces. The sites were far behind the front lines, where soldiers felt relatively safe to gather in large numbers outside in the open, or in buildings that had not been bolstered to defend against attacks.

The Israeli soldiers may have been unaware their location was known, or believed militant groups lacked drones with adequate range to strike or observe them. But Hezbollah has several reconnaissance drones capable of entering Israeli airspace and may have surveilled the base.